My name is ***** ***** I am happy to help. As a firearms instructor, I receive this question a lot. While not impossible, it is very unlikely that the round will "go off". Ammo should, in theory be kept at normal room temperature, but there are studies that have been done where ammo can be raised well above room temps and won't go off. There is another issue though of the heat warping the shell casing and causing an issue with those cartridges when you do plan to fire them. Think about a glass jar with a metal lid that is stuck. You run it under hot water and the lid expands, loosening it. The brass from the casing can warp as well.

I would suggest keeping the gun in a lock box or some shaded area to minimize the exposure to heat.

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Thanks Jim.I am also interested in learning if the gun can trigger by itself as high temperatures may affect trigger mechanism?In other words is it wise to keep a chambered s&w in the car? From the perspective of possible going off by itselfThanks